I've often wondered why I'm happier than most people. After reading a fair bit on the topic I've come to the conclusion that I was just lucky that my upbringing accidentally gave me some very useful tools. I have friends who missed out on them and they make themselves miserable.
Here are the tools I've been able to figure out so far:
I am deliberately grateful for things. There are lots of things we can be grateful for -- I have my eyesight (despite losing some in one eye), I can hear beautiful music (despite gradually going deaf), I have the use of my hands and my legs, I have thousands of books (both on paper and as ebooks), I have a lovely little companion doggie, I can pick up the phone and ring my wonderful parents who are less than an hour's drive away, I live way out in the country where birds and frogs serenade me, I have oodles of amazingly interesting videos to watch and talks to listen to (most downloaded from the net)... and so on. Studies have shown that feelings of gratitude boost enjoyment of life.
I help people when I can. We are social creatures so our brains are wired to generate pleasure when we help others. But this has to be genuine help otherwise it backfires. For example getting frustrated with someone because they don't use your help the way you'd expected, or they don't appear to appreciate it, makes you upset instead of happy because you are actully doing it for yourself instead of for them. It can be difficult, but it's a nice buzz when you get it right.
Find ways to view anything in a positive light. I like to boast that I can see the silver lining in the darkest cloud. It's not entirely true, but it mostly is. I can turn around almost anything to see the positive in it. It has become habit. (I have a friend who does the opposite and often rings me depressed about something trivial that she's worked up into something worse than it should be. That's her habit, and she doesn't realise how it hurts her.)
Some examples make this clearer. Recently I hurt my back (I probably tore a muscle by picking something up the wrong way.) It was astonishingly painful. I could barely walk and couldn't sit at the computer for very long. I turned it into a positive by using it as an excuse to get a lot of reading done, lying in bed.
Here's another example: about a decade ago I was on chemotherapy, lost much of my hair, and was constantly exhausted. I had to pause to catch my breath walking up just a few steps. I turned it into a positive by studying the changes and understanding them. It was fascinating to see how the treatment made me anaemic, and I really enjoyed observing the effects in myself. It gave me greater understanding of, and empathy for, people who are similarly afflicted. It was an opportunity to learn because it doesn't matter how many times we read about something, or are told, we don't truly understand it until we experience it.
Another example: Some time back, I was listening to an interview with a writer who said that when she was little and she hurt herself or some other bad thing happened to her, her mother (who was also a writer) would say to her, "Don't worry dear, it's all grist to the mill." In other words it becomes part of her life experiences. It used to annoy the absolute crap out of her when she was a kid, but now that she's grown up and is a writer too she realises her Mum was exactly right. All those experiences -- good and bad -- give her a wealth that she can draw upon. I feel the same way. One time I was having a scary-looking mole cut out and when the doctor started cutting he said that if I can feel that to let him know and he'll inject more local anaesthetic. I said that it was okay because the pain was interesting. He looked at me funny, but I meant it. It wasn't overpoweringly awful, and it was an experience you don't get very often.
A last example: when I was visiting a friend in New Zealand a few years ago I was helping her by mowing her lawn. When I took the mower from the back lawn around to the front lawn I switched off the mower and was clowning around running down the driveway acting as if it was a racecar. I swerved suddenly near the front gate, but didn't notice the concrete there was mossy. My feet went out from under me and I went down hard, tearing a hole in my pants, badly grazing my knee and one hand. But I focussed on how ridiculous it must have looked and collapsed in laughter punctuated with "Ow, ow!"
I'm not saying that I'm special. I'm just lucky that this has become a habit so I don't even have to try to do it anymore.
Getting something done gives a nice jolt of pleasure, whether it is cleaning the kitchen, or writing a small computer program, or learning a song, or drawing a picture. Weirdly, sometimes I get the greatest pleasure from simple things that take very little effort, but fulfill a need or desire.
Always make sure you get enough. If you don't have sufficient sleep, don't worry about it, catch up later with a nap.
Don't seek it
One very important thing about happiness. I've noticed that seeking it seems to push it away. It's like that tip-of-the-tongue feeling when you're trying to remember a particular word; the harder you try to remember it, the further it recedes from your grasp. The best way to catch the word is to stop trying to catch it and it will pop into your mind later unbidden. Happiness is like that. I've met people who try and try to be happy and it makes them miserable. Don't seek it; trick it into coming to you.
Some things that work for many people, but I don't need:
Sunshine can boost the brain's production of melanin, which can make some people happier. You don't need a lot of sunlight to get this effect. It's why some people feel more unhappy during winter.
A happiness diary can force people to notice the good things in their life. Just note down the good things that have happened to you each day, but not the bad things. It helps the good to loom larger in your view. The bad things will always be there and don't need help, but if your view is mostly uplifting then it sets your frame of mind.
Friends and family
Having contact with friends and family seems to boost happiness for most people. (I enjoy my friends and family, but I don't need that to make me happy -- I love being a hermit. I don't get lonely.)
Physical activity can boost pleasure. Sweeping the floor, going for a walk, dancing, calisthenic exercises. I am not a fan of heavy exercise. I prefer it gentle.
There are a few resources I highly recommend. One is an excellent documentary titled simply "Happy". I haven't been able to find it online but if you ask me I might be able to find a way to get it to you.
Another great resource is Dan Gilbert, a scientist who studies happiness. He's written a very interesting book called "Stumbling on Happiness" which is about how we can find (and lose) happiness in unpredictable ways and what we can learn from that. He's given some TED talks on the topic:
Movies or books that are uplifting, especially comedies, can do wonders. One of my favorite YouTube videos is a Russian one of ordinary people helping each other. It never fails to choke me up and make me feel very happy:
Laughter truly is a marvelous medicine. Even hearing a laugh can cause happiness, especially if it is a baby's laugh:
I love listening to Radiolab episodes. They are almost always uplifting human-interest talks with a good dash of humor. My favorites are the older ones. They have more than 200 of them online and new ones come out every couple of weeks.
Finally, stay away from the mainstream media. Its entire business model is centered on making people fearful and angry. It is very successful at holding audience attention, but it makes people unhappy.